Hyperkeratotic tissue in mammals and the conditions arising therefrom result from abnormal processes within the skin. The top layer of skin, known as the stratum corneum, is composed primarily of cells that are dehydrated keratin protein. In a normal process called keratinization, epidermal cells are gradually pushed to the surface by underlying dermis cells where they exfoliate. In abnormal processes, i.e., when these cells do not exfoliate, they accumulate on the surface to form hyperkeratotic tissue causing discomfort. Hyperkeratotic tissue in mammals includes tylomas (calluses and fissures), helomas (corns), keratoses (papules), and dry skin scales and flakes. Common methods for managing hyperkeratinized tissue are the application of acids in lotion or cream carriers, moisturizing creams or lotions or mechanical scraping. Acids and scraping are disadvantageous because they tend to irritate normal epidermis and moisturizing creams are not effective in reducing hyperkeratotic tissue density.
Calluses and corns, usually found on the feet and hands, are thickened areas of normal skin which have formed to protect underlying bone from excessive weight bearing, pressure or friction. Foot callus appears most commonly on the sole and heel. Hand callus typically forms on the pads of the palm where pressure is most commonly exerted in handling tools and objects. When a callus deposits dead cells at its epicenter, it becomes a corn (heloma), a painful, conical hyperkeratosis. Corns are usually found over toe joints and between the toes and are typically caused by hammertoe, bone spurs or ill-fitting footwear impinging against skin. Calluses and corns cause walking discomfort and are commonly treated by rubbing off the hardened skin with a pumice stone or other scraping device, applying salicylic acid, or, if severe, by bone surgery to correct the underlying pressure point. Salicylic acid is effective for the removal of callus and corns but presents the risk of harming adjacent healthy tissue which is also exfoliated. Salicylic acid is also not recommended for use by the elderly with thinned skin, diabetics or by those with poor circulation or compromised immune systems, as the acid can result in open lesions which are then subject to infection.
Dry skin is a normal consequence of aging and is aggravated by cold, dry or windy climatic conditions. Treatment unusually involves the use of moisturizers after bathing, including petrolatum, lanolin, urea, alpha hydroxy acids, lactic acid or ammonium lactate to reduce scaling and help the skin hold water.